Membrane protein complex of APS reductase and Qmo is present in Desulfovibrio vulgaris and Desulfovibrio alaskensis

Lee R. Krumholz, Luyao Wang, David A. C. Beck, Tiansong Wang, Murray Hackett, Brian Mooney, Thomas R. Juba, Michael J. McInerney, Birte Meyer, Judy D. Wall, David A. Stahl

¹Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USA

²Institute for Energy and the Environment, University of Oklahoma, Norman, OK 73019, USA

³eScience Institute, University of Washington, Seattle, WA 98195, USA

⁴Department of Chemical Engineering, University of Washington, Seattle, WA 98195, USA

⁵Department of Microbiology, University of Washington, Seattle, WA 98195, USA

⁶Center for Microbial Proteomics, University of Washington, Seattle, WA 98195, USA

⁷Department of Biochemistry, University of Missouri, USA

⁸Department of Civil and Environmental Engineering, University of Washington, Seattle, WA 98195, USA

Correspondence
Lee R. Krumholz krumholz{at}ou.edu

Abstract

Due to their adjacent location in the genomes of Desulfovibrio species and their potential for formation of an electron transfer pathway in sulfate-reducing prokaryotes, adenosyl phosphosulfate (APS) reductase (Apr) and quinone-interacting membrane-bound oxidoreductase (Qmo) have been thought to interact together during the reduction of APS. This interaction was recently verified in Desulfovibrio desulfuricans. Membrane proteins of Desulfovibrio vulgaris Hildenborough ΔqmoABCD JW9021, a deletion mutant, were compared to the parent strain using blue-native PAGE to determine whether Qmo formed a complex with Apr or other proteins. In the parent strain of D. vulgaris, a unique band was observed that contained all four Qmo subunits, and another band contained three subunits of Qmo, as well as subunits of AprA and AprB. Similar results were observed with bands excised from membrane preparations of Desulfovibrio alaskensis strain G20. These results are in support of the formation of a physical complex between the two proteins; a result that was further confirmed by the co-purification of QmoA/B and AprA/B from affinity-tagged D. vulgaris Hildenborough strains (AprA, QmoA and QmoB) regardless of which subunit had been tagged. This provides clear evidence for the presence of a Qmo–Apr complex that is at least partially stable in protein extracts of D. vulgaris and D. alaskensis.